Air modulation for waste incinerator

ABSTRACT

An incinerator having a principal combustion chamber and one or more secondary combustion chambers together with the controls that provide a predetermined range of temperature in all chambers to effect continuous and complete combustion of the waste matter placed therein.

United States Patent William M. Anderson AIR MODULATION FOR WASTE INCINERATO 7Clnlms,2l)rawingl"igs.

US. Cl 110/8 A, 110/723 Int. Cl F231 5/00 I ll l I I [2E 1! if L 2! Primary Examiner-Kenneth W. Sprague Attorneys-Wayne H. Lang and Eldon H. Luther ABSTRACT: An incinerator having a principal combustion chamber and one or more secondary combustion chambers together with the controls that provide a predetermined range of temperature in all chambers to effect continuous and complete combustion of the waste matter placed therein.

PATENTED mm :97:

IINVENTOR.

AIR MODULATION FOR WASTE INCINERATOR BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an incinerator arrangement comprising a primary and one or more secondary combustion chambers arranged in series wherein insufficient or starved air" conditions are maintained in the primary incinerator chamber to provide incomplete combustion or gasification of a charge placed therein. Unburned gases produced in the primary combustion chamber are subsequently directed to the secondary combustion chamber where they are mixed with sufficient air and burned completely. Noncombustible e exhaust gases alone are vented to the atmosphere.

2. Description of Prior Art Incineration of waste materials in incinerators of the starved air" type is an effective manner of waste incineration. In a starved air" process, gases from the incineration of solids are produced and only partially burned in a main combustion zone, the unburned gases being subjected to further and complete burning in another combustion zone in the manner shown by U.S. Pat. Nos. 3,491,707 and 3,493,645.

To insure the complete combustion of organic material before waste exhaust gases are vented to the atmosphere, multiple afterburners are frequently utilized to provide combustion of high efficiency. Any interruption in the supply of fuel being charged into the primary combustion chamber of the incinerator leads to a rapid increase in the incinerator chamber temperature as the gaseous mixture passes-through stoichiometric proportions and the combustion of fuel becomes more complete. A resumption in the supply of fuel then frequently results in unsatisfactory operation because of an excessively hot incineration chamber. Excessive smoking and flaring is a common result of charging an incinerator when the temperature within the incineration chamber is excessive.

SUMMARY OF THE INVENTION The present invention relates to a starved air" type incinerator wherein the amount of combustion air supplied is modulated or continuously controlled so as to maintain the desired incineration temperatures within the primary combustion chamber and in the afterbumer during various interruptions in the supply of fuel or changes in the physical nature of the fuel (waste material) being charged.

The above defined combustion control by continuous control or air modulation is achieved by the use of suitable sensing devices in the primary combustion chamber and in the afterburner that control the supply of combustion and cooling air so that a particularly constant incineration temperature is maintained in each chamber in spite of normal operational changes.

BRIEF DESCRIPTION OF THE DRAWING A better understanding of the invention may be had by reference to the drawing in which:

FIG. 1 is a schematic side elevation of an incinerator (partially broken away) which shows a primary and secondary combustion chamber with the controls necessary to make it a completely modulated system, and

FIG. 2 is a front view of the same apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the drawings of the present invention the reference numeral l designates a combustion vessel enclosing a primary combustion chamber 11 having a gas outlet port 12 at one end and a waste loading and access door 14 pivotally supported on hinges at the other. The inner wall of the vessel is suitably insulated by a layer of firebrick which in turn has a coating of castable fire resistant material 22 capable of withstanding temperatures that may range upward to 2500 F.

The bottom of the combustion vessel 10 is adapted to receive several tubes 24 having holes 26 of adequate size to supply the necessary air to the vessel for combustion of a charge placed therein. Other tubes (not shown) may be provided if desired for the supply of overfire air to the combustion chamber 11 in accordance with standard design.

The same tubes 24 may be used for the selective supply or injection of an inert gas whereby oxidation within the combustion chamber Il may be slowed or even stopped at any point of operation by the injection of an inert or noncombustible gas.

The oxygen supply tubes 24 are connected to an outside source of air 25 by the supply duct 27. A control valve 28 continuously movable through an infinite number of settings from full open to full closed position regulates the air flow supplied by source 25 so that a precise modulation of the air flow is achieved at all times.

An outlet stack 40 is connected to the outlet port 12 leading from the main combustion chamber. The stack 40 contains a secondary combustion chamber 25 having a separate burner including a source of fuel and suitable ignition means 43. The air for combustion in the secondary chamber may be supplied through duct 31 by the same source 25 used to supply air to the primary chamber, the air flow through duct 31 being continuously controlled by modulating valve 30 in the same manner as valve 28 controls the air flowing through duct 27.

According to this invention, air for combustion is provided to the primary chamber in considerably less than stoichiometric quantities. Thus, an interruption in the supply of fuel (or waste) to the primary chamber leads to a rapid increase'in temperature therein as the gaseous mixture passes through stoichiometric proportions and combustion becomes more complete. To ensure that conditions in the primary combustion chamber are at all times less than stoichiometric, a limit switch 52 controlling valve 28 through controller 37 is actuated as soon as door 14 is opened to charge the combustion chamber with waste. Thus air entering the primary combustion chamber 11 through door 14 when it is opened to load waste therein is offset by the closure of valve 28. Therefore less than stoichiometric conditions usually prevail in the primary combustion chamber 11 regardless of free air leaking into the chamber 11 through the open door 14. The limit switch 52 provides an on-off" signal to the controller for the valve 28 so that it quickly assumes a full closed or open position in accordance with the disposition of door 14.

The control valve 28 is, in addition, temperature controlled so that it acts in response to a thermocouple 54 in primary chamber or the thermocouple 56 in the secondary chamber. Thus, by the proper setting of controller 37, an increase or decrease of temperature in either the primary or the secondary combustion zones may be used to actuate the valve 28 to control the flow of air to the primary combustion chamber 11. Similarly the control valve 30 modulating air flow through duct 31 is operated in accordance with controller 39 which may be set to move toward an open or closed position in accordance with the signal received from thermocouple 54 or thermocouple 56.

Although both thermocouples 54 and 56 can be adapted to modulate both valves 28 and 30, thermocouple 56 in the primary combustion chamber is usually set to override thermocouple 54 except when further overridden by manual control, timer, or the like indicated at 57. A similar manual control (not shown) may be included in controller 39 however, since such controls are standard in the art and have attained substantial commercial prominence their details are not here shown.

In operation a charge of waste is loaded into the incinerator chamber 11 and ignited in a conventional manner. Door 14 is closed so that the proper amount of air required for gasification and partial combustion of the charge is provided by fan 25 as delivered through valve 28 and openings 26 in pipes 24. Controller 37 for valve 28 isset to support combustion in primary combustion chamber 11 which provides at thermocouple 56, for example, a temperature ranging from 1700" F. to 2000 F. If the controller 37 receives a signal from thermocouple 56 indicating that the temperature of the burning gas from the burning waste material in the primary combustion chamber is increasing towards or exceeds the predetermined set temperature, the control of modulating valve 28 is moved automatically towards a closed position to retard combustion in the primary combustion chamber. As a result of a decreased rate of combustion in chamber 11 the temperature of combustion within the primary combustion chamber lowers to the normal set temperature and the proper quantity of combustible gas is produced for combustion within secondary combustion chamber 25.

The signal produced by the thermocouple 54 and that produced by actuation of the limit switch 52 may be transmitted to the controller 37 by the same or separate circuits in the manner shown by FIG. 1 so that valve 28 responds to either signal produced thereby.

When the door 14 is no longer being opened periodically to permit the loading of fuel into the primary chamber 11, or when the need for continuous modulation of air being supplied through duct 27 is otherwise terminated, the switch 52 on controller 37 for valve 28 may be moved from automatic to manual control.

In normal operation the temperature of the burning gases in the secondary combustion chamber will effect an increase of temperature on thermocouple 56 until it approaches the set point of controller 37. As the temperature increases, the controller 37 causes valve 28 to move gradually toward a closed position to reduce the air being supplied to the primary combustion chamber and the rate of combustion therein. However, when controller 39 for valve 30 receives a similar signal from thennocouple 56 indicating an increase of temperature in chamber 25, valve 30 is set to move toward an open position to supply additional air thereto for more complete combustion as the rate of combustion increases, the temperature in the secondary combustion 25 will similarly rise. An upper temperature limit imposed upon the thermocouple 56 effects a signal which acts through controller 39 and is set to open valve 30 completely to supply an excess of air to the chamber 25 to cool it by dilution.

Similarly a water spray device 62 in chamber 11 may be set to respond to conditions in combustion chamber 25 as detected by thermocouple 64 whereby, for example, an increase of temperature in excess of certain predetermined limits would actuate the spray 62, cool the primary chamber 11 and decrease the temperature at 25. The water spray 62 could otherwise be actuated by a thermocouple in chamber ll, an independent timer, a limit switch on door 14 or the like without departing from the spirit of the invention.

In summary, valve 30 which modulates or gradually changes to regulate the air flowing to chamber 25 is set to open upon an increase of temperature in chambers 11 or 25 to provide additional oxygen to the secondary combustion chamber and insure complete combustion of the gases before they are exhausted to the atmosphere. Conversely, valve 28 modulating air flowing to the primary chamber ll is adapted to close upon an increase of temperature in either chamber H or 25 to reduce the amount of air flowing through duct 27 and the resulting rate of combustion and gasification in the primary chamber 11.

It is evident that various changes may be made without departing from the spirit of the invention, and it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting way.

We claim:

1. An incinerator for burning combustible material comprising a primary combustion chamber having an inlet opening for waste material and an outlet port for gases exhausting therefrom, an outlet stack containing a secondary combustion chamber connected to the outlet port to receive gases exhausting from the primary combustion chamber, movable door means closing t e inlet opening for waste material, an air supply duct connected to the primary combustion chamber, valve means in the air supply duct continuously modulating air flowing to the primary combustion chamber, and means responsive to temperature of the burning waste material controlling the valve means in the air supply duct whereby an increase of temperature effects a decrease of air being supplied to the primary combustion chamber.

2. An incinerator as defined in claim 1 having an air supply duct connected to the secondary combustion chamber, valve means in the air supply duct leading to the secondary combustion chamber, temperature responsive means in the secondary combustion chamber inversely controlling the valve means in the air supply duct thereto whereby an increase of temperature in the secondary combustion chamber effects an increase of air being supplied thereto.

3. An incinerator of the type defined in claim 1 including a cooling means in the primary combustion chamber, and a thermocouple responsive to an increase of temperature in said incinerator actuating the cooling means when the temperature exceeds a predetermined limit.

4. An incinerator of the type defined in claim 1 including a limit switch operable upon opening the movable door, and means responsive to a signal from said limit switch closing the primary air supply valve when said door is opened.

5. Apparatus for incinerating combustible material comprising a primary combustion chamber having an inlet opening for waste material and an outlet port for gases exhausting therefrom, an outlet stack containing a secondary combustion chamber connected to the outlet port to receive gases exhausting from the primary combustion chamber, a door for the inlet opening to the primary combustion chamber, an air supply duct connected to the primary combustion chamber, valve means in said air supply duct continuously modulating air flowing to the primary combustion chamber, a secondary air supply duct connected to the secondary combustion chamber, valve means in the secondary air supply duct arranged to control air flowing the'rethrough, a thermocouple in the secondary combustion chamber detecting the gas temperature therein, and control means responsive to said thermocouple in the secondary combustion chamber simultaneously moving the valve in the secondary air supply duct toward an open position and the valve in the primary air supply duct toward a closed position to provide complete oxidation of the gas produced by the burning waste.

6. An incinerator for burning combustible waste material as defined in claim 5 including a water cooling spray in the primary combustion chamber, a source of water connected to said cooling spray, and means responsive to an increase of temperature in the incinerator actuating the cooling spray in the primary combustion chamber.

7. An incinerator for burning combustible waste material as defined in claim 6 including a limit switch on the door for the inlet opening to the primary combustion chamber, and means closing the modulating valve to the primary combustion chamber when said door is moved to an open" position. 

1. An incinerator for burning combustible material comprising a primary combustion chamber having an inlet opening for waste material and an outlet port for gases exhausting therefrom, an outlet stack containing a secondary combustion chamber connected to the outlet port to receive gases exhausting from the primary combustion chamber, movable door means closing the inlet opening for waste material, an air supply duct connected to the primary combustion chamber, valve means in the air supply duct continuously modulating air flowing to the primary combustion chamber, and means responsive to temperature of the burning waste material controlling the valve means in the air supply duct whereby an increase of temperature effects a decrease of air being supplied to the primary combustion chamber.
 2. An incinerator as defined in claim 1 having an air supply duct connected to the secondary combustion chamber, valve means in the air supply duct leading to the secondary combustion chamber, temperature responsive means in the secondary combustion chamber inversely controlling the valve means in the air supply duct thereto whereby an increase of temperature in the secondary combustion chamber effects an increase of air being supplied thereto.
 3. An incinerator of the type defined in claim 1 including a cooling means in the primary combustion chamber, and a thermocouple responsive to an increase of temperature in said incinerator actuating the cooling means when the temperature exceeds a predetermined limit.
 4. An incinerator of the type defined in claim 1 including a limit switch operable upon opening the movable door, and means responsive to a signal from said limit switch closing the primary air supply valve when said door is opened.
 5. Apparatus for incinerating combustible material comprising a primary combustion chamber having an inlet opening for waste material and an outlet port for gases exhausting therefrom, an outlet stack containing a secondary combustion chamber connected to the outlet port to receive gases exhausting from the primary combustion chamber, a door for the inlet opening to the primary combustion chamber, an air supply duct connected to the primary combustion chamber, valve means in said air supply duct continuously modulating air flowing to the primary combustion chamber, a secondary air supply duct connected to the secondary combustion chamber, valve means in the secondary air supply duct arranged to control air flowing therethrough, a thermocouple in the secondary combustion chamber detecting the gas temperature therein, and control means responsive to said thermocouple in the secondary combustion chamber simultaneously moving the valve in the secondary air supply duct toward an open position and the valve in the primary air supply duct toward a closed position to provide complete oxidation of the gas produced by the burning waste.
 6. An incinerator for burning combustible waste material as defined in claim 5 including a water cooling spray in the primary combustion chamber, a source of water connected to said cooling spray, and means responsive to an increase of temperature in the incinerator actuating the cooling spray in the primary combustion chamber.
 7. An incinerator for burning combustible waste material as defined in claim 6 including a limit switch on the door for the inlet opening to the primary combustion chamber, and means closing the modulating valve to the primary combustion chamber when said door is moved to an ''''open'''' position. 